This application claims the priority of German Application No. 199 01 277.6, filed Jan. 15, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for authenticating a spare vehicle key for use with a vehicle.
A method of this type is known from European Patent document EP 0 7.88 946 A. In this reference, with the aid of a separate programming unit located outside the vehicle, data specific to a part of the vehicle are retrieved from a central station, transmitted from the central station to the programming unit, and transferred from the latter to the vehicle. The data are then decoded in the vehicle. Although double coding is used some of the time, problems may arise with the known method if the separate programming unit is misused.
Overall, it should be noted that the general trend to increase protection against theft and break-ins runs counter to the customer service requirement of being able to open and move a vehicle when the original key is not present, for example if the original key has been lost or inadvertently locked inside the vehicle. The problem becomes even more acute when burglar-proof glass is used.
The goal of the invention is therefore to create a method of the type referred to above that is easy to perform and use, as well as being protected against misuse.
The invention achieves this goal by providing a method for authenticating a spare key to be used in a vehicle in the absence of the regular key. The spare key is provided with an identification number that is transmitted to, and checked by, a central station. The spare key is authenticated by an authorization signal sent by the central station to the vehicle.
The essential point of the invention is authentication of the spare key by the central station. Since the identification number of the spare key is transmitted to, and checked by, the central station, obvious misuse of a spare key that has been lost for example, as soon as this fact is communicated to the central station, is recognized and transmission of the authorization signal from the central station to the vehicle is prevented.
Advantageous embodiments of the invention are explained in greater detail in the description of the method based on the figures.
Advantageously, at least some of the data transmissions, such as from the spare key to the central station or from the central station to the vehicle are encoded. In particular, the data transmissions are encoded with a random number. In a particular preferred embodiment, bidirectional data traffic occurs wherein the data transmission takes place in one direction followed by transmission of a confirmation signal in an opposite direction. Further advantageously, the bidirectional data traffic in the one direction takes place based on a public key and the decoding at the central station takes place based on private key.
In a particularly advantageous embodiment, the transmission of the spare key identification number to the central station is performed by the vehicle itself, to which the spare key identification number was previously transmitted.
Also advantageously, data transmission can take place via telephony.
In another advantageous embodiment, before the actual data transmission occurs, a receiver is activated by the spare key.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.